Coronary Artery Disease

Coronary heart disease is a condition in which the arteries that supply the heart become hardened and narrowed over time. This results in a decreased supply of blood and oxygen to the heart muscle, the myocardium. This can cause serious complications, such as heart attacks and heart failure.

Coronary artery disease usually has a slow onset, often beginning during adolescence, but only becoming symptomatic much later in life, in middle age. 1 The main symptom is chest pain or pressure that can radiate to the jaw, shoulder, back or arms. Treatment depends on the severity of symptoms and typically involves managing other health conditions that are contributing to CAD, making lifestyle changes, using medications and, in some cases, undergoing a procedure to widen the blood vessels of the heart. These treatments can help to prevent severe complications.

Deoxygenated blood is transported to the heart from the body via the vena cava, a vein, entering through the right atrium and then traveling to the right ventricle. From here, the blood flows to the lungs, where it is oxygenated before returning to the heart, entering the left atrium and then passing into the left ventricle. From the left ventricle, oxygenated blood leaves the heart for the body via the aorta, an artery.

More than 3,000 gallons of blood pass through the heart every day; 1 it is one of the only muscles in the body that never rests. The heart muscle itself is supplied with blood by the left and right coronary arteries, which branch off from the aorta near where the aorta leaves the left ventricle of the heart. The left main coronary artery supplies the left side of the heart with blood, while the right coronary artery supplies the right side. 2

If either of the coronary arteries becomes narrowed or blocked, the heart muscle does not get enough blood to supply its needs, potentially causing stable or unstable angina or heart attacks. 3

Symptoms of coronary artery disease may include:

• Angina, i.e. short-lived episodes of chest pain
• Shortness of breath
• Nausea
• Cold sweat
• Dizziness.

In severe cases, a heart attack may occur. Chest pain, caused by an insufficient supply of blood, is the most characteristic symptom of coronary artery disease. The severity of the symptoms vary according to the extent to which the arteries are affected, and how much oxygen the heart needs at the time the symptoms appear.

Shortness of breath typically manifests if the coronary artery disease is causing acute heart failure or chronic heart failure, each of which cause fluid to build up in the lungs. Acute and chronic heart failure are not the same as a heart attack, which is technically known as myocardial infarction.

A heart attack is a medical emergency and requires immediate medical care. Not all people experiencing a heart attack will have all the symptoms. The location and nature of the pain experienced during a heart attack can differ between men and women, with women more likely to feel pain in the lower chest, upper back or abdomen and to experience other symptoms such as nausea and lightheadedness. 4 Not all heart attacks involve intense chest pain, and not all heart attacks are sudden, but may come on more slowly. 5

The chest pain caused by a heart attack may: 4 6 7

• Feel like burning, crushing, squeezing or fullness
• Be felt in the jaw, neck, arm, upper back or abdomen
• Cause an abnormal heartbeat
• Last for more than 20 minutes.

Other symptoms of a heart attack include: 4 5 6 7

• Nausea and vomiting
• Pale, mottled and clammy skin
• Sweating
• Lightheadedness or dizziness
• Chills
• Shortness of breath
• Anxiety and restlessness
• Weakness.

Not everyone will experience all of these symptoms. Medical assistance is required as soon as possible in the case of a heart attack, even if not all of these symptoms are present. For more information, see this resource on heart attacks.

Angina often feels like pressure or squeezing in the chest. The pain is often located in the center of the chest and may spread to the arms and jaw. It is typically described as similar to a heart attack in sensation.

Angina tends to disappear with rest and worsen if the affected person engages in activity. It is often brought on by exercise. The pain is most likely to happen during or after exertion, eating, stress or excitement, or sudden exposure to cold conditions. 8 Some people may experience angina while resting. Depending on the onset of symptoms and some other criteria, it is possible to differentiate various forms of chest pain, related to angina, caused by CAD, including:

• Stable angina
• Unstable angina
• Myocardial infarction
• Sudden cardiac death.

Unstable angina and myocardial infarction cannot be differentiated by symptoms. Instead, a doctor will rely on laboratory findings and ECG.

Good to know: If an episode of angina takes more than about ten minutes to pass, comes on for the first time or without warning, or if there is no identifiable cause, it is known as unstable angina. 8 9 For more information, see this resource on unstable angina.

Unstable angina pectoris is a medical emergency. Although the symptoms are similar, it is not necessarily a heart attack. However, it indicates that the affected person is at high risk of having a heart attack, and medical treatment should be sought as soon as possible. 9

Coronary artery disease is slightly more common in men than women and is most common in middle-aged and older adults. Important risk factors include diabetes, high blood pressure, smoking, drinking alcohol, obesity and having a family member who has or had coronary artery disease. In the majority of cases, the underlying cause of coronary artery diseases is atherosclerosis.Risk factors for coronary artery disease can be divided into two main groups: modifiable and non-modifiable. Non-modifiable factors cannot be changed, while modifiable factors can.

Non-modifiable risk factors for coronary artery disease include: 3 10

• Advancing age
• Male sex
• A family history of coronary artery disease.

Men are at increased risk of developing coronary artery disease after the age of 45, while women are at increased risk from the age of 55. 10 People with a family history of coronary artery disease are particularly at risk if the affected relative is a parent or a sibling.

Risk factors for coronary artery disease that can be modified include: 3 10

• Smoking
• Physical inactivity
• Being overweight
• High blood levels of LDL cholesterol
• Low blood levels of HDL cholesterol
• Diabetes and/or high blood glucose levels and/or insulin resistance
• High blood pressure
• A diet low in Vitamins C, D and E, low in fruit and vegetables, and low in Omega 3s.

Sleep apnea, high stress levels, alcohol consumption and a history of preeclampsia can also increase the chances of coronary artery disease developing. For ways to modify some of these risk factors, see below. For more information on the factors that affect someone’s chance of developing coronary artery disease or other heart conditions, see this resource on cardiovascular disease risk factors.

Most cases of coronary artery disease are caused by atherosclerosis, a condition in which a fatty, waxy substance known as atherosclerotic plaque builds up on the inside of the arteries, 10 forming atheromas. Atheromas are made up of fatty materials, proteins, waste materials from the blood and cholesterol. Calcium may also accumulate in atheromas. Atheromas are usually hard and fibrous on the outside. ref1 Technically, atherosclerosis can affect any artery in the body; 3 the form affecting the coronary arteries is known as coronary atherosclerosis.

If atheromas develop in a coronary artery, they can protrude and interrupt the flow of blood through the artery. Atheroma can harden or burst. If they harden, blood flow through the artery is reduced. If they burst, a blood clot may form on the surface of the atheroma and interrupt blood flow. A blood clot that forms in a coronary artery is called a coronary thrombus. 1 If a blood clot forms, angina can occur. If the atheroma or blood clot is large enough, blood flow through the artery may be totally cut off, causing a coronary occlusion and leading to a heart attack. Atheromas can rupture even if they are not large enough to obstruct blood flow; the thrombus that forms if this happens can further narrow or even block the artery, causing the heart muscle to cramp. For more information, see our resource on atherosclerosis.

A heart attack or angina may also occur if the artery spasms and becomes narrower due to the irritation caused by a thrombus. The interruption of blood flow through the artery, whether it is caused by an atheroma, a clot, or a spasm, causes a condition known as myocardial ischemia. 8 It is ischemia that causes the chest pain characteristic of coronary artery disease. The point at which ischemia occurs changes, depending on where in the coronary artery the flow is interrupted, 11 how large the interruption is and how much oxygen the heart muscle needs at the time. Ischemia causes acute coronary syndromes such as unstable angina and heart attack. 3 ref11

In a small number of cases, coronary artery disease can result from a spasm of the coronary artery. This is known as variant angina or Prinzmetal angina. These spasms can be caused by stress, exposure to cold, smoking, the use of drugs that cause blood vessels to narrow, such as epinephrine and norepinephrine, and the use of stimulant drugs such as cocaine or nicotine. 12 It may also result from congenital heart defects or physical damage to the coronary arteries. In some cases, systemic lupus erythematosus can cause coronary artery disease.

In some people, coronary artery disease is the result of endothelial dysfunction in the coronary arteries. Endothelial dysfunction occurs when the artery does not expand to accommodate an increased demand for blood in the heart muscle, such as during exertion. 3 Arterial dissection, where a tear develops in an artery’s lining, an embolism, aneurysm or vasculitis can also cause coronary artery disease. 11

Diagnosis is based on the symptoms and a physical examination. An electrocardiogram (ECG or EKG) or an exercising ECG/EKG – useful for showing heart damage that only occurs when exercising – may also be used. Blood tests for cholesterol levels and blood sugar levels can also be helpful. Rarely, a magnetic resonance image (MRI) can be performed on the heart to examine the vessels.

There are a number of tests that may be ordered if coronary artery disease is suspected. An electrocardiogram, known as an ECG or EKG, records the electrical activity in the heart, measures the heart’s rhythm and speed and may show signs of heart muscle damage.

Stress testing is related to the ECG and is done in conjunction with it, as the affected person undergoes an ECG while exercising. This test will show any changes and abnormalities in heart rate, blood pressure and heart rhythm.

An echocardiography uses sound waves to create a moving picture of the heart and to show whether the valves and chambers are working properly. It can show areas where blood flow or muscle function is compromised.

Cardiac angiography, where dye is injected into the heart blood vessels via a cardiac catheter and X-rays are taken, may help identify areas of narrowing or blockage in the heart arteries. 10

Treatment depends on the specific symptoms being experienced and their severity. For people with mild, predictable chest pain symptoms, treatment will generally involve thinning the blood to prevent blockages and taking medication to help open up the blood vessels. As the condition progresses, it may be necessary to have cardiac catheterization – the insertion of a tube through the leg blood vessels into the heart blood vessels– in order to widen narrowed or blocked blood vessels with a stent, a small wire cage. Eventually, some people may need bypass surgery.

The goal of all treatment for coronary artery disease is to: 3

• Reduce the heart’s workload by controlling blood pressure
• Improve blood flow by stretching narrowed arteries
• Prevent complications and symptoms, such as angina and heart attacks
• Slow or stop the development of atheromas
• Lower the risk of blood clots

There are many ways to do this, including basic lifestyle changes, medication and surgical options.

Making basic lifestyle changes is one of the first steps in the long-term treatment of coronary artery disease. These changes include adopting a healthy diet, limiting alcohol consumption, quitting smoking, learning to manage stress, maintaining a healthy weight and getting enough exercise.

Alcohol consumption should be limited to one drink a day for women and two for men. One drink is twelve liquid ounces of beer, five ounces of wine or one and a half ounces of liquor.

Smoking should be discontinued immediately upon receiving a diagnosis of coronary artery disease, if not before, and if the affected person does not smoke, they should not start. Quitting smoking considerably decreases the risk of developing CAD.

It is also important to positively manage stress and responses to stressful events, especially those involving anger. Yoga, meditation and stress-management courses may be useful for this.

Physical activity should be increased to at least two and a half hours a week, if not more. For people who have not been exercising, a very gradual increase in the intensity of the exercise is recommended, and activities such as walking, swimming, cycling and rowing may be best. Also, strength training helps increase general strength levels, 3 making more aerobic types of exercise such as those listed more enjoyable, which in turn improves an affected person’s likelihood of sticking to an exercise regime. 13 The affected person’s body weight should be kept within, or lowered to, a BMI of between 18 and 25. ref3 10

Various foods promote heart health, and these should be included in the diet of people who have received a diagnosis of coronary artery disease. Dietary changes can be an important first step towards lowering cholesterol and high blood pressure. Foods that are beneficial to people with CAD include: 3 10

• Fish high in omega 3, such as salmon, mackerel, sardines or tuna
• Fresh fruit and vegetables
• Complex carbohydrates in the form of whole grains, which contain soluble and insoluble fibres to assist digestive function and stabilize blood glucose levels
• Legumes
• Moderate amounts of monounsaturated and polyunsaturated fats, which can be found in nut and seed-derived oils, nuts and seeds, avocado, and soy products such as tofu.

Foods that should be consumed only in extreme moderation include red meat, palm and coconut oils, and high-sugar foods, snacks and drinks. These foods tend to be high in saturated fats and trans fats, which increase LDL cholesterol. Salt and high-salt foods should also be consumed only in very small amounts.

Along with lifestyle changes, medication is another long-term method of managing coronary artery disease. Medications commonly prescribed include: 14 15

• Antiplatelet drugs, such as aspirin, which reduce the likelihood of developing a blood clot around an atheroma
• Statins, which lower LDL cholesterol
• ACE inhibitors and angiotensin II inhibitors, which lower blood pressure and have other protective effects for the heart
• Beta blockers to slow the heart rate, lower blood pressure and reduce the heart’s demand for oxygen
• Calcium-channel inhibitors, which slow heart rate and widen blood vessels
• Nitrates, such as nitroglycerin, which cause the arteries to relax, reducing the blood pressure and reducing the heart’s workload

All of these medications have side effects, and it is important to discuss the various options and potential combinations thoroughly with the physicians who prescribe them.

In some cases, surgical measures may be needed to widen narrowed or blocked arteries, or to bypass the areas affected by arteriosclerotic blockages. The two most common procedures to do this are the percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG).

This procedure is also known as a percutaneous transluminal coronary angioplasty. It is less invasive than CABG and effective in more than 80 percent of cases. 3 However, it is not always possible. ref3

The procedure involves a small surgical balloon being attached to a catheter and threaded into an artery in the wrist or thigh. It is then directed to the aorta and from there into the affected coronary artery. The balloon is moved into place at the point where the artery is narrowed or blocked and then inflated. The pressure of the inflation stretches the artery and flattens the atheroma. 3

Once the artery is widened and the atheroma compressed, a wire mesh tube called a stent is inserted into the widened stretch. Most stents are impregnated with a drug that prevents the artery from blocking again. Because these impregnated stents can increase the risk of blood clots, the person who has undergone the PCI will need to take an antiplatelet drug and aspirin for between three to 12 months after the procedure and continue taking aspirin for the rest of their life.

This procedure is often referred to as bypass surgery or coronary artery bypass surgery. It is an invasive procedure and requires a short hospital stay of about a week. It is more likely to result in post-surgical complications, such as stroke or heart attack, than a PCI. In this procedure, a section from another artery or vein is used to replace the affected section of coronary artery. Leg veins are often used, or arteries from the forearm. Arterial grafts seldom develop CAD. 3

Preventing coronary artery disease involves lifestyle and dietary changes. Being physically active, losing weight, ceasing to smoke and excluding alcohol from the diet can all help. Good management of other medical conditions, such as high blood pressure, diabetes and high cholesterol levels can also help to prevent the progression of coronary artery disease.

• CAD
• Coronary heart disease
• Ischemic heart disease

Q: What should people who have the non-modifiable risk factors for CAD do?
A: If you have non-modifiable risk factors, it’s a good idea to work on improving the modifiable factors by making dietary changes, quitting smoking and increasing fitness levels. It may also be a good idea to visit a doctor in order to discuss medication or other management methods. In this way, blood cholesterol levels and hypertension can be managed, reducing the heart’s workload and lowering the chance of developing CAD or complications from CAD.

Q: Which age groups are particularly affected by CAD?
A: Between 5 and 9 percent of all people older than 20 years of age are affected by the most common form of CAD, coronary atherosclerosis. Men and women are affected by CAD, but before menopause, women are protected by high estrogen levels. This leads to men appearing to be affected at younger ages, and this leads to the appearance of higher rates among men. After the age of 55, however, the mortality rate among men decreases. Among people aged 75 and older, more women than men have CAD. However, CAD is the leading cause of mortality among both men and women in the developed world. 3

Q: How quickly does quitting smoking benefit people with CAD or the risk factors for CAD?
A: Once a person has quit smoking, their risk of stroke or heart attack decreases within weeks. Within about two years, the risk of CAD, stroke and heart attacks decreases to the same as that of someone who has never smoked. 16

Q: How is CAD related to strokes?
A: Coronary heart disease and stroke share many risk factors. 17 There are two main types of stroke, hemorrhagic stroke and ischemic stroke. Ischemic strokes result from the blockage of a blood vessel in the brain by an atheroma. Atherosclerosis is a common cause of ischemic strokes. 18 Hemorrhagic strokes are more commonly associated with high blood pressure. 19